Dan,

My impression is that a cape needs to hang down the back, either in conjunction with or separate from a mantle. If this is so, I think the images Mart and I posted qualify as mantles. However, I'm not especially well-versed in historical fashion, so I could well be wrong.

The half-circle mantle, cape, what-have-you of Roger II of Sicily has these dimensions: H. 1,46 m; L. 3,45 m. At 57 1/2 inches long, I can see how this might hinder movement. On the other hand, Dan also has valid points. Unfortunately we don't have any historic visual record, and the literary record isn't an ironclad description, so we are left with alternate interpretations. We simply can't be more definitive about the robe and / or mantle being worn over armor, or the method of painting the shield for the period around the 3rd Crusade.